R&D Report 1986-08 : The measurement of large values of airborne sound insulation. R.Walker The requirements for and the measurement of airborne sound insulation between areas in a broadcasting centre are discussed. In particular, the high values of insulation required in some cases and the difficulties of measurement are described. One method which has been used for such measurements, using explosive charges, has been investigated in detail. Some of the results obtained in the past using this method have been questionable and the possible reasons for errors are reported. It is concluded that the high peak level of sound pressure generated by the explosion, measured at 160dB re 20 uPa at a distance of 6m from the explosion, has been responsible for overloading the measuring instrumentation. In recovering from this short-lived but serious overloading, the instrumentation has sometimes given erroneous results. The non-linearity of sound propagation at these sound pressure levels may also be theoretically significant although, in practice, no such effects have been positively identified. An alternative method of measuring high values of sound insulation without requiring such high sound pressure levels is described and the results of an evaluation are given. This method however, in exchanging high sound pressure levels for measurement duration, may take much longer to carry out than the older method.
